This filter can be used to change the URL that Caldera Forms submits the form against.
If in your WordPress setting’s you do not use HTTPS for your site URL, but are loading the form on a page that uses HTTPS, the browser may reject submission due to mixed protocols, since the API URL will be insecure. This is one of the many reasons you should use SSL/ HTTPS for your whole site. If not, you can use this filter to change the submission URL for that form:
Submit Caldera Form Against An Alternative Destination
If you would like to submit the form against another URL, bypassing all of Caldera Forms processing, you can using this filter.
Where Does This Code Go?
When using WordPress hooks to customize Caldera Forms or other plugins you should not modify the plugin files, or you will lose your changes when you update the plugin. Instead you should create a small plugin to hold the custom code. It's easy, learn how here.
Technically you can add the custom code to your theme's functions.php, but then you will not be able to change your theme and keep these customizations.